Cutter insert gum modification method and apparatus

Abstract

Described herein are several methods and apparatuses for treating a cutter tool adapted to be used in tunnel boring operations. In one form, an initial cutter member blank is formed and heat treated prior to a laser cladding process. An alloy is often applied to the surface of the cutter blank adjacent to the cutting elements by the cladding process whereby the cladding process has insufficient heat transfer from the cladding process to reduce hardness properties of the inserts and/or the cutter blank. In one example a fabric-like material defines the region of the exterior hard surface.

Therefore I claim: 
     
       1. A method of treating a cutter tool, the method comprising:
 a) preheating the tool to at least 350° F. 
 b) identifying a gum region positioned in the outer portion of the cutter tool, 
 c) employing laser cladding to the gum region adjacent to cutting elements, 
 d) whereas the cutting elements have a hardness higher than that of the surrounding gum region adjacent thereto and the heat transfer to the cutting elements from the laser cladding process is insufficient to materially alter the hardness of said cutting elements and the gum region is more resistant to erosive wear. 
 
     
     
       2. The method as recited in  claim 1  whereby the cladding process applies a cladding material at a thickness greater than 0.030 of an inch. 
     
     
       3. The method as recited in  claim 1  whereby the heat transfer to the cutting elements does not raise the temperature of the cutting elements above 900° F. 
     
     
       4. The method as recited in  claim 1  further comprising the step of brazing the cutting elements into cavities within the cutter tool. 
     
     
       5. The method as recited in  claim 1  whereby a distance of a laser beam in the laser cladding process to the gum region is adjusted to a consistent width during application on the gum region. 
     
     
       6. A method of treating a cutter tool, the method comprising the steps of:
 a) providing a cutter tool that is heat treated with an outer region defining a plurality of cavities adapted to receive cutting elements, 
 b) inserting cutting elements into each of the cavities, 
 c) pre heating the cutter tool to approximately 350° F.-650° F., 
 d) engaging a laser cladding process whereby an alloy powder is applied to the cutter tool outer surface adjacent to the cutting elements. 
 
     
     
       7. The method as recited in  claim 6  where the Rockwell hardness of the cutter tool is between 32 and 44 when forming the plurality of cavities. 
     
     
       8. The method as recited in  claim 7  whereby the cutting elements are press fit into the cavity regions. 
     
     
       9. The method as recited in  claim 6  whereby the alloy powder is introduced into the laser as it passes along the cutter tool perimeter surface. 
     
     
       10. The method as recited in  claim 6  whereby the alloy powder is positioned on the cutter tool outer surface and the laser transfers heat thereto. 
     
     
       11. The method as recited in  claim 6  whereby the material immediately surrounding the cutting elements in the cutter tool defines a gum region having a hardness at least 20 Rockwell units lower than the cutting elements. 
     
     
       12. The method as recited in  claim 11  whereby the Rockwell hardness of the laser cladded layer on the cutter tool outer surface is at least 20 Rockwell hardness higher than the cutter tool. 
     
     
       13. A cutter tool having a perimeter region with a plurality of cavities with cutting elements fixedly positioned in said cavities, the cutter tool having a
 gum region with a plurality of cavities therein retaining said cutting elements, the gum region having a surface region, a hardened layer cladded to the surface region where the hardened layer is cladded to the surface region when the cutter tool is preheated above 350° F. and heat is applied to an alloy powder to form the hardened layer whereby the cutting elements are not affected by the heat is applied to an alloy powder and the metallurgical hardness properties of the cutting elements is preserved 
 whereby hardened elements of the hardened layer and the cutting elements have a Rockwell hardness at least 20 units greater than the gum region. 
 
     
     
       14. The cutter tool as recited in  claim 13  where the temperature of the cutting elements during the heat transfer to the alloy powder does not increase above 900° F. 
     
     
       15. The cutter tool as recited in  claim 13  where the Rockwell hardness of the cutting elements in the hardened layer is at least 30 units greater than the gum region. 
     
     
       16. The cutter tool as recited in  claim 15  where the surface region is comprised of a matrix composition mixed with a tungsten carbide material. 
     
     
       17. The cutter tool as recited in  claim 13  where the hardened layer is not more than ⅛ of an inch in thickness. 
     
     
       18. The cutter tool as recited in  claim 16  where the Rockwell hardness of the cutter tool is not more than 44 when forming the plurality of cavities in the gum region. 
     
     
       19. The cutter tool as recited in  claim 16  where the cutting elements are placed in the cavities after the hardened layer is formed. 
     
     
       20. The cutter tool as recited in  claim 16  where the cutting elements are placed in the cavities prior to the application of alloy powder to form the hardened layer.